My earlier U.S. Pat. Nos. 3,080,265 and 3,380,461 describe a system for cleaning a conduit--an underground pipe or even an open trench--of a waste-disposal system. A nozzle is mounted on the downstream end of a high-pressure conduit. This nozzle has at least one backwardly open water-ejecting aperture. Water supplied under high pressure to this nozzle, therefore, is ejected backwardly to displace the nozzle along in the conduit to be cleaned. As it moves forward the nozzle loosens sludge deposits and the like inside the conduit, in particular on the floor thereof. Backward withdrawl of the nozzle, while still spraying, effectively scoops the loosened deposits up and allows them to be flushed away. Such a system has replaced more complex mechanical scraping devices, as it allows a conduit to be cleaned with a relatively simple tool, and without running the risk of damaging the interior of the conduit.
Many of the known systems have the disadvantage that much of the water sprayed out by the nozzle does not serve for cleaning. Since sewage conduits almost never run completely full, their upper walls and the upper portions of their side walls normally are relatively clean. Thus the high-pressure streams directed against these upper walls serve no function. Closing the apertures directed upwardly has not, however, proven effective, as the nozzle then normally reorients itself with the apertures pointing upwardly, so that none of the apertures is directed at the lower wall. Forming the nozzle of flattened shape will orient it better inside the conduit, but will make passing it around bends or the like somewhat more difficult. What is more, when such a flattened nozzle turns over it is necessary to withdraw the entire nozzle with the hose to reorient it.